Groundwater is a critical resource in semi-arid regions like Morocco's Guire Basin, yet pollution and overexploitation threaten its sustainability. This study evaluates the groundwater quality of the Guire aquifer (Eastern High Atlas) using an integrated approach combining hydrochemical, isotopic (delta O-18, delta H-2, delta C-13), multivariate statistical, and Geographic Information System (GIS) analyses alongside the Water Quality Index (WQI). Sixteen wells were monitored for physicochemical parameters (pH: 7-7.9; EC: 480-3004 mu S/cm; BOD5: 1.03-30.5 mg/L; COD: 10.2-45.75 mg/L) and major ions, revealing widespread exceedances of Moroccan standards for Cl-, HCO3-, Mg2+, Ca2+, and NH4+. WQI classified 81% of samples as "Poor" to "Unsuitable for drinking" (WQI: 51-537), driven by elevated Cl-, Na+, and SO42- from Triassic evaporite dissolution and NO3- (up to 45 mg/L) from agricultural runoff. Stable isotopes (delta O-18: -7.73 parts per thousand to -5.08 parts per thousand; delta H-2: -66.14 parts per thousand to -44.20 parts per thousand) indicate Atlantic-influenced recharge at 900-2200 m altitudes, with a delta O-18-delta H-2 slope of 5.93 reflecting evaporation during infiltration. Strontium (Sr2+/Ca2+: 0.0024-0.0236) and bromide (Br/Cl: 8.47 x 10(-5)-9.88 x 10(-4)) ratios further confirm evaporitic dominance over anthropogenic contamination. This work provides actionable insights for policymakers, advocating for targeted restrictions on fertilizers, enhanced monitoring near evaporite zones, and artificial recharge initiatives. By linking geogenic/anthropogenic contamination to governance strategies, this study advances sustainable groundwater management in semi-arid regions.